氢化物冷阱捕集法原子吸收测定海水中无机锡

THE DETERMINATION OF INORGANIC TIN IN SEAWATER WITH ATOMIC ABSORPTION SPECTROPHOMETRY AND HYDRIDE COLD TRAP

采用硼氢化纳还原法将海水中无机锡还原为挥发性锡化氢,氮为载气将锡化氢从反应器吹出,并于液氮冷阱中捕集,捕集后将锡化氢载入氢焰原子化器进行原子吸收测定。对该还原反应、氢化物转移、捕集及原子化实验条件进行了详细研究。实验结果表明:该法中可氢化元素As、Sb、Se等超过被测物浓度200倍时亦无明显干扰,检出限为0.0060μg/dm^3,对0.050μg/dm^3 Sn浓度的样品变异系数为±8％。标准曲线表明,在0—0.050μg/dm^3 Sn浓度范围内有理想的线性关系。对海水介质测定,该法所作校准曲线与蒸馏水介质具有相同的斜率,采用NaOH共沉淀预富集可提高灵敏度5—10倍,便于海水样品保存,总回收率95％以上。

The method is based on the reduction of inorganic tin to volatile SnH4 which is bubbled out by carrier gas of pure nitrogen, trapped in a liquid nitrogen trap and then swept to hydrogen flame quartz atomizer to measure its atomic absorbance. The hydride generation, transportation, trap and aromisation were studied. The optimum conditions selected are as follows: reactive acidity, 4μ10-3M HCl, The amoumt of NaBH4, 2% 2ml in 100ml sample; gas flow of nitrogen, 300-400ml/min; gas flow of hydrogen, 220-250 ml/min, the trap of U-tube packed with silanized glass wool. There are no obvious interferences of elements such as As, Se, Sb when their concentrations are less than 200 times of Sn. The detection limit is 0.0060μg/dm3 and the variation coefficient at tin level of 0.050μg/dm3 is ±8% The calibration curve shows an ideal line in the concentration of 0 000-0.050μg/dm3 Sn with the same slope for both distilled water and sea water With coprecipitation by addition of NaOH to prcconcentration of inorganic tin, the sample storage is facilitated and the sensitivity can be improved by a factor of 5-10 with a recovery of above 95%